Vortex light interference device and method

Abstract

The present invention provides a vortex light interferometry device and method, relating to the field of optical system technology. The device includes a circularly polarized light generating unit, a first interferometry unit, a second interferometry unit, a vortex beam generating unit, a first dove prism, a second dove prism, a first CCD camera, and a second CCD camera. When demonstrating the separation of orbital angular momentum of multimode hybrid vortex light, the vortex beam generating unit is disposed at the two interferometry light paths of the first interferometry unit to convert both interferometry light beams into vortex beams. The first dove prism and the second dove prism are disposed at the light paths of the first transmitted light and the first reflected light, respectively, and the first dove prism and the second dove prism are rotated relative to each other by an angle of π / 2. The first CCD camera and the second CCD camera are used to image the first and second output lights, respectively. The present invention enables intuitive demonstration of vortex light interference and the separation of orbital angular momentum of multimode hybrid vortex light.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and in particular to a vortex light interference device and method. Background Art

[0002] Vortex beams are known for their unique phase vortex properties. Their wavefront exhibits a spiral shape, with a phase singularity at its center. This results in zero light intensity at the center, resulting in a ring-shaped light intensity distribution. Vortex beams are currently becoming a hot topic of research, with various vortex beams, such as Laguerre-Gaussian beams, Bessel beams, Airy vortex beams, and perfect vortex beams, being gradually realized and widely used in various fields, including astronomy, microscopy, particle manipulation, optical communications, and quantum entanglement. Therefore, it is particularly important to understand the basic concepts and characteristics of vortex beams, how they are generated, and the characteristics and principles of their interference with different light sources.

[0003] Currently, there are devices that can generate vortex light and realize vortex light interference demonstration. However, problems with related technologies restrict the development of vortex light interference research. On the one hand, existing vortex light interference devices usually only focus on realizing interference demonstration between vortex lights of different modes, and cannot realize the separation demonstration of the orbital angular momentum of multi-mode mixed vortex light.

[0004] On the other hand, there are many challenges in generating interference images with CCD cameras, which seriously affect subsequent research by technicians in this field. Existing CCD cameras lack the ability to process the generated interference images. Even though some studies have performed image processing on interference images, existing image processing algorithms are difficult to fully and accurately extract the multi-scale features and dynamic change information in the vortex light interference images. In addition, since the vortex light's pattern, orbital angular momentum and other characteristics change continuously over time during the propagation and interference process, traditional methods find it difficult to effectively capture this dynamic information and make accurate predictions. For example, in the real-time analysis scenario of multi-mode mixed vortex light, traditional technologies are unable to timely and accurately distinguish the evolution process of vortex light of different modes, which limits the study of the complex behavior of vortex light. Summary of the Invention

[0005] In order to address the deficiencies in the prior art, the purpose of the present invention is to provide a vortex light interference device and method to address the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned object, a first aspect of the present invention provides a vortex light interference device, comprising: a circularly polarized light generating unit, a first interference unit, and a second interference unit;

[0007] a circularly polarized light generating unit, for generating circularly polarized light;

[0008] a first interferometer unit, configured to implement Mach-Zehnder interference based on the circularly polarized light generated by the circularly polarized light generating unit, and transmit the combined light beam to the second interferometer unit;

[0009] The second interference unit includes a first reflector, a first beam splitter prism, a second reflector, a third reflector, and a second beam splitter prism; the first reflector reflects the light beam transmitted by the first interference unit to the first beam splitter prism, the first beam splitter prism splits the light beam into a first transmitted light and a first reflected light, the first transmitted light enters the second beam splitter prism after being reflected by the second reflector, and the first reflected light enters the second beam splitter prism after being reflected by the third reflector; the second beam splitter prism generates a first output light and a second output light, the first output light includes a light beam obtained by reflecting the first transmitted light through the second beam splitter prism and a light beam obtained by transmitting the first reflected light through the second beam splitter prism, and the second output light includes a light beam obtained by transmitting the first transmitted light through the second beam splitter prism and a light beam obtained by reflecting the first reflected light through the second beam splitter prism;

[0010] It also includes a vortex beam generating unit, a first dove prism, a second dove prism, a first CCD camera, and a second CCD camera. When the multi-mode hybrid vortex light orbital angular momentum separation is demonstrated, the vortex beam generating unit is arranged at the two interference light paths of the first interference unit, and is used to convert both interference light beams into vortex beams. The first dove prism and the second dove prism are respectively arranged at the light paths of the first transmitted light and the first reflected light, and the first dove prism and the second dove prism are relatively rotated by an angle of π / 2. The first CCD camera and the second CCD camera are respectively used to image the first outgoing light and the second outgoing light to obtain an interference image; wherein the first CCD camera and the second CCD camera are both embedded with a neural network chip;

[0011] The neural network chip is integrated with a convolutional neural network model, which includes a multi-scale pyramid convolution module, a feature enhancement module and a recurrent memory fusion module; the multi-scale pyramid convolution module is composed of multiple groups of convolution layers with convolution kernels of different sizes in parallel; the interference image passes through different convolution layers to obtain feature maps of different scales, and the obtained feature maps of different scales are fused to obtain interference image features; in the feature enhancement module, the interference image features are first globally averaged pooled to obtain a global feature vector for each channel; then the attention weight is calculated through two fully connected layers; finally, the attention weight and the interference image feature are multiplied to obtain an enhanced feature map; the recurrent memory fusion module is composed of multiple long short-term memory network units connected end to end, and the enhanced feature map is input into the long short-term memory network unit in chronological order, wherein the long short-term memory network unit includes a forget gate, an input gate, an output gate and a memory unit.

[0012] Preferably, the first interference unit includes a first polarization beam splitter prism, a fourth reflector, a fifth reflector, a second polarization beam splitter prism, a first quarter wave plate, and a third polarization beam splitter prism; the first polarization beam splitter prism splits the circularly polarized light generated by the circularly polarized light generating unit into a second transmitted light and a second reflected light, the second transmitted light enters the second polarization beam splitter prism after being reflected by the fourth reflector, the second reflected light enters the second polarization beam splitter prism after being reflected by the fifth reflector, the second transmitted light and the second reflected light are combined at the second polarization beam splitter prism, and then pass through the first quarter wave plate and the third polarization beam splitter prism in sequence and are transmitted to the first reflector.

[0013] Preferably, the circularly polarized light generating unit includes a solid laser, an attenuation plate, a half-wave plate, a beam expansion unit, and a second quarter-wave plate. The laser generated by the solid laser is attenuated in sequence by the attenuation plate, the polarization state is changed by the half-wave plate, and the beam is expanded by the beam expansion unit to obtain linearly polarized light. The second quarter-wave plate converts the linearly polarized light into circularly polarized light and outputs it to the first interference unit. The beam expansion unit includes a first focal length plano-convex lens and a second focal length plano-convex lens.

[0014] Preferably, the vortex beam generating unit includes a first vortex beam generating unit and a second vortex beam generating unit, the first vortex beam generating unit includes a first q wave plate and a third quarter wave plate, the second vortex beam generating unit includes a second q wave plate and a fourth quarter wave plate, and the orders of the first q wave plate and the second q wave plate are different; the order of the first q wave plate is an even number, and the order of the second q wave plate is an odd number.

[0015] Preferably, the long short-term memory network unit takes the enhanced feature map and the hidden state of the previous moment as input. In the long short-term memory network unit, the forget gate calculation is first performed, then the input gate calculation is performed, and the candidate memory unit is generated. Then the memory unit is updated according to the forget gate calculation result, the input gate calculation and the candidate memory unit to determine the current moment information, and finally the hidden state output at the current moment is determined through the output gate.

[0016] Preferably, in the cyclic memory fusion module, except for the last long short-term memory network unit, the hidden states output by other long short-term memory network units will serve as the input of the long short-term memory network unit at the next moment.

[0017] A second aspect of the present invention, based on the vortex light interferometer device provided in the first aspect, further provides a vortex light interferometer method, comprising:

[0018] Two vortex beam generating units of different orders are respectively arranged at the first transmission path and the first reflection path of the first interference unit, so that the first interference unit outputs a dual-mode mixed vortex beam;

[0019] The first dove prism is arranged between the first beam splitter prism and the second reflector, the second dove prism is arranged between the third reflector and the second beam splitter prism, and the first dove prism and the second dove prism are rotated relative to each other by an angle of π / 2;

[0020] The first CCD camera is arranged at the position where the first outgoing light of the second beam splitter prism emerges, and the first outgoing light is imaged to obtain a first interference image; the second CCD camera is arranged at the position where the second outgoing light of the second beam splitter prism emerges, and the second outgoing light is imaged to obtain a second interference image;

[0021] An interference image is obtained, pre-processed, and then input into a convolutional neural network model to output a vortex light interference analysis map. The interference image is input into the convolutional neural network model, and the interference image features are first extracted through a multi-scale pyramid convolution module. Then, the interference image features are enhanced through a feature enhancement module to output an enhanced feature map. Finally, a cyclic memory fusion module is used to output a vortex light interference analysis map.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention can achieve vortex light interference and intuitively demonstrate the separation of the orbital angular momentum of multimode mixed vortex light. The circularly polarized light generation unit and the first interferometer unit can achieve vortex beam interference and simultaneously generate a dual-mode mixed vortex beam, which is input to the second interferometer unit. The second interferometer unit, based on a Dove prism and a Mach-Zehnder interferometer, can separate the orbital angular momentum components of the dual-mode mixed vortex beam. The output light is imaged using a CCD camera to clearly show the separated single-mode vortex beam fringes.

[0024] The present invention embeds a neural network chip in each CCD camera and utilizes the multi-scale pyramid convolution module in the convolutional neural network model, employing convolution kernels of different sizes to operate in parallel. This module comprehensively captures multi-scale features from image details to overall contours, enabling the model to more accurately identify characteristics such as vortex light patterns and orbital angular momentum, demonstrating significant advantages in analyzing complex multi-mode mixed vortex light interference images. Simultaneously, the recurrent memory fusion module uses LSTM units to learn long-term dependencies between image sequences. Combined with enhanced contextual awareness, adaptive memory updates, and dynamically adjusted output mechanisms, it effectively captures the dynamic changes in vortex light interference and can accurately predict interference fringe movement and pattern transitions, providing a powerful tool for dynamic process research.

[0025] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 A schematic structural diagram of a vortex light interferometer provided by the present invention;

[0028] Figure 2 This is a theoretical simulation diagram of the interference between a plane wave and a vortex beam;

[0029] Figure 3 This is a theoretical simulation diagram of the interference between spherical waves and vortex beams;

[0030] Figure 4 for A theoretical simulation of vortex beam interference.

[0031] Figure 5 A flow chart of a vortex light interference method provided by the present invention;

[0032] Among them, 1. solid laser; 2. attenuation plate; 3. half-wave plate; 4. first focal length plano-convex lens; 5. second focal length plano-convex lens; 6. second quarter-wave plate; 7. first polarization beam splitter prism; 8. fourth reflector; 9. fifth reflector; 10. second polarization beam splitter prism; 11. first quarter-wave plate; 12. third polarization beam splitter prism; 13. first reflector; 14. first beam splitter prism; 15. second reflector; 16. second beam splitter prism; 17. third reflector; 18. second CCD camera. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] The embodiments of the present invention, such as Figure 1 As shown, a vortex light interference device is first provided, including: a circularly polarized light generating unit, a first interference unit, and a second interference unit.

[0035] The circularly polarized light generating unit is used to generate circularly polarized light.

[0036] The first interference unit is used to realize Mach-Zehnder interference based on the circularly polarized light generated by the circularly polarized light generating unit, and transmit the combined light beam to the second interference unit.

[0037] The second interference unit includes a first reflector 13, a first beam splitter prism 14, a second reflector 15, a third reflector 17, and a second beam splitter prism 16; the first reflector 13 reflects the light beam transmitted by the first interference unit to the first beam splitter prism 14, and the first beam splitter prism 14 splits the light beam into a first transmitted light and a first reflected light. The first transmitted light enters the second beam splitter prism 16 after being reflected by the second reflector 15, and the first reflected light enters the second beam splitter prism 16 after being reflected by the third reflector 17; the second beam splitter prism 16 generates a first output light and a second output light. The first output light includes a light beam obtained by reflecting the first transmitted light through the second beam splitter prism 16, and a light beam obtained by transmitting the first reflected light through the second beam splitter prism 16. The second output light includes a light beam obtained by transmitting the first transmitted light through the second beam splitter prism 16, and a light beam obtained by reflecting the first reflected light through the second beam splitter prism 16. For the convenience of description, the optical path of the first transmitted light is referred to as the first transmission path (t' path), and the optical path of the first reflected light is referred to as the first reflection path (r' path).

[0038] The device also includes a vortex beam generating unit, a first Dove prism, a second Dove prism, a first CCD camera, and a second CCD camera 18. When the multi-mode mixed vortex light orbital angular momentum separation is demonstrated, the vortex beam generating unit is arranged at the two interference light paths of the first interference unit, and is used to convert both interference light beams into vortex beams. The first Dove prism and the second Dove prism are respectively arranged at the light paths of the first transmitted light and the first reflected light, and the first Dove prism and the second Dove prism are rotated relative to each other by an angle of π / 2. The first CCD camera and the second CCD camera 18 are respectively used to image the first outgoing light and the second outgoing light.

[0039] The first interference unit includes a first polarization beam splitter prism 7, a fourth reflector 8, a fifth reflector 9, a second polarization beam splitter prism 10, a first quarter-wave plate 11, and a third polarization beam splitter prism 12. The first polarization beam splitter prism 7 splits the circularly polarized light generated by the circularly polarized light generating unit into a second transmitted light and a second reflected light. The second transmitted light is reflected by the fourth reflector 8 and then enters the second polarization beam splitter prism 10. The second reflected light is reflected by the fifth reflector 9 and then enters the second polarization beam splitter prism 10. After the second transmitted light and the second reflected light are combined at the second polarization beam splitter prism 10, they pass through the first quarter-wave plate 11 and the third polarization beam splitter prism 12 in sequence and are transmitted to the first reflector 13. The first polarization beam splitter prism 7 and the second polarization beam splitter prism 10 are polarization beam splitters used to decompose circularly polarized light into vertically polarized light and horizontally polarized light. The transmission path is horizontally polarized light, and the reflection path is vertically polarized light. For ease of description, the optical path of the second transmitted light is referred to as the second transmission path (t-path), and the optical path of the second reflected light is referred to as the second reflection path (r-path). The first quarter-wave plate 11 converts the linearly polarized light beam split by the second polarization beam splitter prism 10 into circularly polarized light, thereby causing the two light beams to interfere. The third polarization beam splitter prism 12 serves as an analyzer, allowing only horizontally polarized light to pass through for imaging on a CCD camera. Mach-Zehnder interference can be achieved by adjusting the first polarization beam splitter prism 7, the fourth reflector 8, the fifth reflector 9, and the second polarization beam splitter prism 10.

[0040] The circularly polarized light generation unit includes a solid-state laser 1, an attenuation plate 2, a half-wave plate 3, a beam expansion unit, and a second quarter-wave plate 6. The solid-state laser 1 uses a 532nm solid-state laser, and the output light is vertically polarized light. The attenuation plate 2 is arranged after the solid-state laser 1 to reduce the intensity of the light incident on the CCD camera to prevent lens burn. The half-wave plate 3 is a half-wave plate with an operating wavelength of 532nm and is used to change the polarization state of the output light from the solid-state laser. The beam expansion unit includes a first focal length plano-convex lens 4 and a second focal length plano-convex lens 5. In this embodiment, the first focal length plano-convex lens 4 is a plano-convex lens with a focal length of 25mm, and the second focal length plano-convex lens 5 is a plano-convex lens with a focal length of 250mm. The combination of the first focal length plano-convex lens 4 and the second focal length plano-convex lens 5 can expand the light beam. The second quarter-wave plate 6 is used to convert linearly polarized light into circularly polarized light, thereby achieving the generation of circularly polarized light.

[0041] The vortex beam generating unit consists of a q-wave plate and a quarter-wave plate, which can be placed in the optical path as needed to generate a vortex beam. In this embodiment, the vortex beam generating unit includes a first vortex beam generating unit and a second vortex beam generating unit. The first vortex beam generating unit includes a first q-wave plate and a third quarter-wave plate, and the second vortex beam generating unit includes a second q-wave plate and a fourth quarter-wave plate. To intuitively demonstrate the separation of orbital angular momentum of multimode hybrid vortex light, the order m of the first and second q-wave plates is different. The order m of the first q-wave plate is even (in this embodiment, the order m of the first q-wave plate is 2), while the order of the second q-wave plate is odd (in this embodiment, the order m of the second q-wave plate is 3).

[0042] The device also includes a plano-convex cylindrical lens. This lens is positioned in front of the first and / or second CCD cameras during the multimode hybrid vortex light orbital angular momentum separation demonstration to convert the first and / or second outgoing light beams into Hermite-Gaussian beams. In this embodiment, the plano-convex cylindrical lens has a focal length of 50 mm.

[0043] In addition to demonstrating the separation of orbital angular momentum of multimode hybrid vortex light, the device can also perform demonstrations of interference between a vortex beam and a plane wave, interference between a vortex beam and a spherical wave, and interference between vortex beams of different modes. In these demonstrations, a CCD camera can be placed between the first and second interferometers (i.e., between the third polarization beam splitter prism 12 and the first reflector 13), and experimental demonstrations can be conducted using the circularly polarized light generation unit and the first interferometer. In addition to the first and second CCD cameras, a third CCD camera can be added and removably placed between the first and second interferometers. Alternatively, the first CCD camera can be designed to be removable. When demonstrating interference experiments such as interference between a vortex beam and a plane wave, interference between a vortex beam and a spherical wave, or interference between vortex beams of different modes, the first CCD camera can be placed between the first and second interferometers. When demonstrating the separation of orbital angular momentum of multimode hybrid vortex light, the first CCD camera can be placed in the optical path of the first outgoing light.

[0044] In some embodiments, in order to facilitate the understanding of the basic concepts and characteristics of the vortex beam, understand the generation method of the vortex beam, and master the characteristics and principles of its interference with different lights, it is preferred to combine a solid laser 1, an attenuation plate 2, a half-wave plate 3, a first focal length plano-convex lens 4, a second focal length plano-convex lens 5, a second quarter-wave plate 6, a first polarization beam splitter prism 7, a fourth reflector 8, a fifth reflector 9, a second polarization beam splitter prism 10, a first quarter-wave plate 11, a third polarization beam splitter prism 12, a first reflector 13, a first beam splitter prism 14, a second reflector 15, a second beam splitter prism 16, a third reflector 17, and a second CCD camera 18, that is, Figure 1The various structures shown in the figure are designed as fixed elements fixed to the bottom plate of the device; the first q-wave plate, the second q-wave plate, the first quarter-wave plate, the second quarter-wave plate, the plano-convex cylindrical lens, the third focal length plano-convex lens (for demonstration of interference between vortex beam and spherical wave), and the first CCD camera are designed as magnetic elements that can flexibly change their positions to meet the needs of different experimental demonstrations.

[0045] The following introduces different experimental demonstration methods.

[0046] Vortex beam generation:

[0047] A Q-plate, a polarization modulation device made of nematic liquid crystal, can exchange the spin angular momentum and orbital angular momentum of a light beam. By controlling the uneven distribution of the principal axes of the liquid crystal molecules across a cross-section, it forms a local half-wave plate at each point on the cross-section, introducing a geometric spiral phase into the modulated light. This imparts orbital angular momentum to the output beam, creating a vortex beam. Therefore, placing a Q-plate at an appropriate location in the optical path (different placements for different types of interference) can generate a vortex beam.

[0048] Interference of a vortex beam with a plane wave:

[0049] The electric field expression of the vortex beam is: ,in is the amplitude, for simplicity, let it be a constant, is the angular quantum number of the vortex beam. The expression for the plane wave is , Let be a constant. , then the intensity distribution I1 after the vortex beam interferes with the plane wave is:

[0050] ;

[0051] in, E P The electric field expression representing the interference between a vortex beam and a plane wave is: E P * express E P The conjugate of θ is the azimuth angle, x is the rectangular coordinate, and λ is the wavelength, where 2π / λ=k, and k is the wave vector. According to the above formula, the interference pattern of the plane wave and the vortex beam can be simulated. When When Figure 2 shown.

[0052] based on Figure 1In order to achieve interference between a vortex beam and a plane wave, the device shown requires placing a quarter-wave plate (first quarter-wave plate) rotated to 45 degrees and a first q-wave plate with m=2 between the first polarization beam splitter prism 7 and the fourth reflector 8, i.e., the second transmission path (t-path). The first quarter-wave plate is used to convert linearly polarized light into circularly polarized light, and the first q-wave plate is used to convert circularly polarized light into a vortex beam. At this time, the t-path beam is a vortex beam, and the r-path beam is a plane wave. By adjusting the first polarization beam splitter prism 7, the fourth reflector 8, the fifth reflector 9, and the second polarization beam splitter prism 10, the plane wave and the vortex beam can interfere with each other, forming interference fringes. By placing a first CCD camera between the third polarization beam splitter prism 12 and the first reflector 13, the interference pattern can be observed in the CCD software connected to the first CCD. The theoretical diagram of the interference pattern is shown as follows: Figure 2 shown.

[0053] Interference of vortex beam and spherical wave:

[0054] The expression of spherical wave is ,in, and is a constant, the expression for the plane wave is ,make , then the intensity distribution I2 after the vortex beam interferes with the spherical wave is:

[0055] ;

[0056] in, E s The electric field expression representing the interference between the vortex beam and the spherical wave is: E P * express E P The conjugate of , θ is the azimuth angle, x and y are the coordinates of the rectangular coordinate system, λ is the wavelength, where 2π / λ=k, k is the wave vector. According to the above formula, the interference pattern of the spherical wave and the vortex beam can be simulated. When When Figure 3 shown.

[0057] based on Figure 1In order to achieve interference between a vortex beam and a plane wave, the device shown requires placing a quarter-wave plate (third quarter-wave plate) rotated to 45 degrees and a first q-wave plate with m=2 between the first polarization beam splitter prism 7 and the fourth reflector 8, i.e., the second transmission path (t path). A third focal length plano-convex lens with a focal length of 50 mm is placed between the fifth reflector 9 and the second polarization beam splitter prism 10, i.e., the second reflection path (r path). The third focal length plano-convex lens is used to convert the plane wave into a spherical wave. At this time, the t-path beam is a vortex beam, and the r-path beam is a spherical wave. By adjusting the first polarization beam splitter prism 7, the fourth reflector 8, the fifth reflector 9, and the second polarization beam splitter prism 10, the spherical wave and the vortex beam can be interfered to form interference fringes. By placing a first CCD camera between the third polarization beam splitter prism 12 and the first reflector 13, the interference pattern can be observed. The theoretical diagram of the interference pattern is shown as follows: Figure 3 shown.

[0058] Interference between vortex beams of different modes:

[0059] Consider the simplest case, that is, combining two vortex beams with equal intensity, and assume that their angular quantum numbers are and , then the vortex beams after their coaxial combination are The complex amplitude E is:

[0060] ;

[0061] It can be seen that the cross-sectional light intensity distribution satisfies the following formula:

[0062] ;

[0063] The above formula shows that the cross-sectional intensity distribution of the vortex beam after the two-way equal-intensity beam combination is about the angular coordinate It is also easy to understand that the light field after the dual-path vortex beams are combined with equal intensity has a petal-like structure, and the number of petals is equal to Moreover, the phase distribution of the vortex beam after the two single-mode equal-intensity beams are combined is different from that of the single-mode beams, but is the result of the interaction between the two spiral phases.

[0064] based on Figure 1 In order to achieve dual-path vortex beam interference, the device shown in the figure requires a quarter-wave plate (third quarter-wave plate) rotated to 45 degrees and a first q-wave plate with m=2 to be placed between the first polarization beam splitter prism 7 and the fourth reflector 8, i.e., the second transmission path (t path); and a quarter-wave plate (fourth quarter-wave plate) rotated to 45 degrees and a second q-wave plate with m=3 to be placed between the fifth reflector 9 and the second polarization beam splitter prism 10, i.e., the second reflection path (r path). At this time, the t-path beam is The vortex beam of r-path is By adjusting the first polarization beam splitter prism 7, the fourth reflector 8, the fifth reflector 9, and the second polarization beam splitter prism 10, the two-way vortex beam of equal intensity can be combined to form interference fringes. A first CCD camera is placed between the third polarization beam splitter prism 12 and the first reflector 13 to observe the interference pattern. The theoretical diagram of the interference pattern is shown in FIG. Figure 4 shown.

[0065] Multi-mode hybrid vortex optical orbital angular momentum separation:

[0066] Based on the above demonstration of interference between vortex beams of different modes, the orbital angular momentum separation demonstration of multi-mode hybrid vortex light can be further realized. Two identical Dove prisms (i.e., the first Dove prism and the second Dove prism) are placed on the t' path and the r' path respectively, and the two Dove prisms rotate relative to each other. This means that when the light beam passes through the first dovetail prism, the light field distribution in the cross section perpendicular to the z axis will be flipped relative to the x axis, and when the same light beam passes through the second dovetail prism, the light field distribution in the cross section perpendicular to the z axis will be flipped relative to the x axis, and rotated by angle.

[0067] Since the angular quantum number is The vortex beam contains the phase factor When the vortex beam passes through the second Dawes prism, the spiral phase factor becomes , and the spiral phase factor becomes when it passes through the first prism Obviously, when the vortex beam with the same angular quantum number passes through the first and second prisms, it will produce Phase difference.

[0068] The first beam splitter prism 14, the second reflector 15, the third beam splitter prism 16, and the third reflector 17 constitute a Mach-Zehnder interferometer. The principle of separating the orbital angular momentum of a vortex beam by a Mach-Zehnder interferometer with Dove prisms on both arms can be understood through "destructive interference". Define two operators and , which acts on the vortex light field When , the following formula is satisfied:

[0069] ;

[0070] ;

[0071] Where, is an expression in polar coordinates, which can be expressed as:

[0072] ;

[0073] Where r is the polar diameter.

[0074] The above formula shows that Acting on the light field makes the light field relative to the straight line Symmetry; and When acting on a light field, it will rotate the light field Angle. Therefore, the action operator of the reflector can be expressed as , the operator of the effect of the Dove prism on the light field It can be expressed as:

[0075] .

[0076] The outgoing light at A, i.e., the first outgoing light, includes the first reflected light of the r' path transmitted through the second beam splitter prism 16, and the first transmitted light of the t' path reflected through the second beam splitter prism 16. In the r' path, the incident light is reflected by the first beam splitter prism 14, resulting in a half-wave loss. The phase change is then reflected by the third reflector 17 to produce Phase change, the transmission through the second prism produces a fixed phase change and phase delay , and then a fixed phase change occurs through the second beam splitter prism 16 In the t' path, the incident light is transmitted by the first beam splitter prism 14 to produce a fixed phase change , the transmission passes through the first dovetail prism to produce a fixed phase change , which is then reflected by the second mirror to produce Phase change, then reflected by the second beam splitter prism 16 to produce a fixed phase change Therefore, when the incident vortex beam has a spiral phase term When , the phase difference between the two beams of light entering the CCD at A through the r' path and the t' path is .

[0077] Similarly, when the incident vortex beam has a spiral phase term When the second outgoing light at B is , the phase difference between the two beams of light on the r' path and the t' path is .

[0078] The above analysis shows that for the angular quantum number After the vortex beam with an even number passes through the Mach-Zehnder interferometer with Dove prisms on both arms, the phase difference between the two beams at point B is An odd multiple of this produces destructive interference, and the electric field vector at point B is , so the light field energy will only be output from A. Similarly, for the angular quantum number For an odd-numbered vortex beam, at point A, the phase difference between the two beams is An odd multiple of this produces destructive interference, and the electric field vector at A After passing through the Mach-Zehnder interferometer, the light field energy is output from point B. It should also be noted that the light beam emitted from point A undergoes three reflections during its transmission, resulting in the order of the vortex beam or the sign of the orbital angular momentum it carries being reversed; while the light beam emitted from point B undergoes two and four total reflections during its transmission, respectively, leaving the order of the output beam or the sign of the orbital angular momentum it carries unchanged. Specifically, for the light beam emitted at point A, the light beam transmitted through the t' path, after passing through the first beam splitter prism 14, is reflected once by the first dove prism, once by the second reflector 15, and once by the second beam splitter prism 16, and then emerges from point A. The light beam transmitted through the r' path is reflected once by the first beam splitter prism 14, once by the third reflector 17, once by the second dove prism, and then transmits through the second beam splitter prism 16 before emerging from point A. For the light beam emitted from point B, the light beam transmitted through the t' path, after passing through the first beam splitter prism 14, is reflected once by the first dove prism, once by the second reflector 15, and then transmits through the second beam splitter prism 16 before emerging from point B. The light beam transmitted through the r' path is reflected once by the first beam splitter prism 14, once by the third reflector 17, once by the second dove prism, and once by the second beam splitter prism 16 before emerging from point B.

[0079] When the dual-mode hybrid vortex beam When incident, after passing through the Mach-Zehnder interferometer equipped with a Dove prism, +2nd order and +3rd order single-mode vortex beams can be observed at points A and B, respectively.

[0080] When demonstrating the separation of the orbital angular momentum of a multimode hybrid vortex beam, the first CCD camera is placed at point A, where the first outgoing light emerges. A first and second Dove prisms, rotated relative to each other by an angle of π / 2, are placed on the t' and r' paths, respectively. The five-petal interference pattern originally observed between the third polarization beam splitter prism 12 and the first reflector 13 disappears. At this point, a plano-convex cylindrical lens with a focal length of 50 mm is placed in front of the first and second CCD cameras, respectively. The vortex beam transforms into a Hermite-Gaussian beam, and the pattern becomes a striped pattern tilted upward to the right. The first CCD camera displays two stripes, while the second CCD camera displays three stripes. This indicates that the separation of the orbital angular momentum components of the multimode hybrid vortex beam has been successfully achieved.

[0081] In this embodiment, a neural network chip is embedded in both the first and second CCD cameras. When the first CCD camera images the first emitted light to obtain a first interference image, or when the second CCD camera images the second emitted light to obtain a second interference image, the interference image is obtained, pre-processed, and then input into a convolutional neural network model to output a vortex light interference analysis map. The interference image is first input into the convolutional neural network model, and the interference image features are first extracted using a multi-scale pyramid convolution module. The interference image features are then enhanced using a feature enhancement module to output an enhanced feature map. Finally, a cyclic memory fusion module is used to output a vortex light interference analysis map.

[0082] Specifically: Preprocessing of interference images includes adaptive multi-scale image enhancement, feature normalization, and multi-scale sampling and splicing. , first decompose it into sub-images of different scales , =1,2,…,n, where n represents the number of scales. The decomposition process can be achieved by the Gaussian pyramid algorithm, i.e. ,in Are different scales Then, for each scale sub-image, , calculate its local contrast The local contrast is calculated by taking the pixel The standard deviation of the pixel values in the local area centered and mean The ratio of is obtained, the formula is , is a very small constant used to avoid the denominator being zero.

[0083] According to the local contrast , adaptively adjust the pixel value of the sub-image. The enhanced sub-image The calculation formula is ,in is the enhancement coefficient corresponding to scale s, which is adaptively adjusted according to the importance of features at different scales and the overall image situation. Finally, the enhanced sub-images are merged back into the complete enhanced image. , enhanced image is the interference image after preprocessing.

[0084] The multi-scale pyramid convolution module in the convolutional neural network model is used to extract interference image features. The multi-scale pyramid convolution module consists of multiple groups of convolution layers with different sizes of convolution kernels in parallel. 3, 5 5, 7 7 convolution kernel as an example, for the input preprocessed interference image , through different convolution kernels 、 、 Convolution is performed separately to obtain feature maps of different scales 、 、 .

[0085] ; ; ;in, The pixel position on the feature map, is the pixel position within the convolution kernel. Then these different scale feature maps are spliced and fused into interference image features according to the channel. The interference image features are , ,This multi-scale convolution method can more comprehensively capture the features of ,images at different scales.

[0086] In the feature enhancement module, the interference image features are first Perform global average pooling to obtain the global feature vector of each channel , the formula is ,in and are the height and width of the feature map, Indicates the number of channels. Then through two fully connected layers and Calculating attention weights , first go through Dimensionality reduction, then Dimensional increase, the formula is , , ,in Is the sigmoid function, used to map the weight value to the (0,1) interval. Finally, the attention weight is multiplied by the interference image feature to obtain the enhanced feature map , the formula is , which can highlight the key characteristic channels related to the vortex optical properties.

[0087] In the recurrent memory fusion module, the recurrent memory fusion module is composed of multiple long short-term memory network units connected end to end, and the long short-term memory network unit includes a forget gate , input gate , output gate and memory units Each LSTM network unit receives the hidden state of the previous moment , the enhanced feature map at the current moment as input.

[0088] In the long short-term memory network unit, the forget gate calculation is performed first, and the forget gate Determine the memory unit of the previous moment Which information is retained in the formula is .in, is the weight matrix of the forget gate, Indicates that the hidden state of the previous moment and the current enhanced feature map are spliced in a specific dimension. is the bias of the forget gate, It is a sigmoid function that maps the output value to the (0, 1) interval. The closer the value is to 1, the higher the degree of retention of the corresponding information.

[0089] Then the input gate is calculated and candidate memory units are generated. Control the degree to which the current input information enters the memory unit and generate candidate memory units at the same time The input gate calculation formula is , the candidate memory unit calculation formula is .in, 、 is the corresponding weight matrix, 、 is the bias, It is a hyperbolic tangent function that maps the output value to the (-1, 1) interval.

[0090] The memory unit is updated based on the calculation results of the forget gate, the input gate calculation, and the candidate memory unit to determine the current moment information. The formula for memory unit update is: ;in, Represents element-by-element multiplication, which determines which parts of the memory unit at the previous moment are retained based on the output of the forget gate, and adds the new information at the current moment determined by the input gate and the candidate memory unit.

[0091] Output Gate Determines which information in the memory cell is used to generate the output at the current moment, the hidden state at the current moment The output gate calculation formula is , the hidden state calculation formula is ;in, is the weight matrix of the output gate, is the bias, which controls the output of the memory unit information through the output gate. The hidden state is obtained by processing the memory unit using the hyperbolic tangent function and multiplying it with the output gate result. Except for the last LSTM unit, the hidden state output by each LSTM unit will serve as the input of the next LSTM unit.

[0092] The hidden state of the last LSTM unit output The features containing time series information can record the changes of vortex light interference features over time. In order to obtain the final vortex light interference analysis diagram, the hidden state needs to be By mapping it to a specific dimension through a fully connected layer and converting it into an image, we can obtain a vortex light interference analysis map. This vortex light interference analysis map includes the characteristics of vortex light patterns, orbital angular momentum, and other characteristics that change over time.

[0093] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A vortex light interference device, characterized in that: include: a circularly polarized light generating unit, a first interference unit, and a second interference unit; a circularly polarized light generating unit, for generating circularly polarized light; a first interferometer unit, configured to implement Mach-Zehnder interference based on the circularly polarized light generated by the circularly polarized light generating unit, and transmit the combined light beam to the second interferometer unit; The second interference unit includes a first reflector, a first beam splitter prism, a second reflector, a third reflector, and a second beam splitter prism; the first reflector reflects the light beam transmitted by the first interference unit to the first beam splitter prism, the first beam splitter prism splits the light beam into a first transmitted light and a first reflected light, the first transmitted light enters the second beam splitter prism after being reflected by the second reflector, and the first reflected light enters the second beam splitter prism after being reflected by the third reflector; the second beam splitter prism generates a first output light and a second output light, the first output light includes a light beam obtained by reflecting the first transmitted light through the second beam splitter prism and a light beam obtained by transmitting the first reflected light through the second beam splitter prism, and the second output light includes a light beam obtained by transmitting the first transmitted light through the second beam splitter prism and a light beam obtained by reflecting the first reflected light through the second beam splitter prism; It also includes a vortex beam generating unit, a first dove prism, a second dove prism, a first CCD camera, and a second CCD camera. When the multi-mode hybrid vortex light orbital angular momentum separation is demonstrated, the vortex beam generating unit is arranged at the two interference light paths of the first interference unit, and is used to convert both interference light beams into vortex beams. The first dove prism and the second dove prism are respectively arranged at the light paths of the first transmitted light and the first reflected light, and the first dove prism and the second dove prism are relatively rotated by an angle of π / 2. The first CCD camera and the second CCD camera are respectively used to image the first outgoing light and the second outgoing light to obtain an interference image; wherein the first CCD camera and the second CCD camera are both embedded with a neural network chip; The neural network chip is integrated with a convolutional neural network model, which includes a multi-scale pyramid convolution module, a feature enhancement module and a recurrent memory fusion module; the multi-scale pyramid convolution module is composed of multiple groups of convolution layers with different sizes of convolution kernels in parallel; the interference image passes through different convolution layers to obtain feature maps of different scales, and the obtained feature maps of different scales are fused to obtain interference image features; in the feature enhancement module, the interference image features are first globally averaged pooled to obtain a global feature vector for each channel; then the attention weight is calculated through two fully connected layers; finally, the attention weight is multiplied by the interference image feature to obtain an enhanced feature map; the recurrent memory fusion module is composed of multiple long short-term memory network units connected end to end, and the enhanced feature map is sequentially input into the long short-term memory network unit in chronological order, wherein the long short-term memory network unit includes a forget gate, an input gate, an output gate and a memory unit; In the recurrent memory fusion module, except for the last long short-term memory network unit, the hidden states output by other long short-term memory network units will serve as the input of the long short-term memory network unit at the next moment.

2. A vortex light interference device according to claim 1, characterized in that: The first interference unit includes a first polarization beam splitter prism, a fourth reflector, a fifth reflector, a second polarization beam splitter prism, a first quarter wave plate, and a third polarization beam splitter prism; the first polarization beam splitter prism splits the circularly polarized light generated by the circularly polarized light generating unit into a second transmitted light and a second reflected light, the second transmitted light is reflected by the fourth reflector and enters the second polarization beam splitter prism, the second reflected light is reflected by the fifth reflector and enters the second polarization beam splitter prism, the second transmitted light and the second reflected light are combined at the second polarization beam splitter prism, pass through the first quarter wave plate and the third polarization beam splitter prism in sequence, and are transmitted to the first reflector.

3. A vortex light interference device according to claim 1, characterized in that: The circularly polarized light generating unit includes a solid-state laser, an attenuation plate, a half-wave plate, a beam expansion unit, and a second quarter-wave plate. The laser light generated by the solid-state laser is attenuated by the attenuation plate, the polarization state is changed by the half-wave plate, and the beam is expanded by the beam expansion unit to obtain linearly polarized light. The second quarter-wave plate converts the linearly polarized light into circularly polarized light and outputs it to the first interference unit. The beam expansion unit includes a first focal length plano-convex lens and a second focal length plano-convex lens.

4. A vortex light interference device according to claim 1, characterized in that: The vortex beam generating unit includes a first vortex beam generating unit and a second vortex beam generating unit. The first vortex beam generating unit includes a first q-wave plate and a third quarter-wave plate. The second vortex beam generating unit includes a second q-wave plate and a fourth quarter-wave plate. The orders of the first q-wave plate and the second q-wave plate are different; the order of the first q-wave plate is an even number, and the order of the second q-wave plate is an odd number.

5. The vortex light interference device according to claim 1, wherein: The long short-term memory network unit takes the enhanced feature map and the hidden state of the previous moment as input. In the long short-term memory network unit, the forget gate calculation is first performed, and then the input gate calculation is performed, and a candidate memory unit is generated. Then the memory unit is updated according to the forget gate calculation result, the input gate calculation and the candidate memory unit to determine the current moment information, and finally the hidden state output at the current moment is determined through the output gate.

6. A vortex light interference method, characterized in that: A vortex light interferometer device according to any one of claims 1 to 3, comprising: Two vortex beam generating units of different orders are respectively arranged at the first transmission path and the first reflection path of the first interference unit, so that the first interference unit outputs a dual-mode mixed vortex beam; The first dove prism is arranged between the first beam splitter prism and the second reflector, the second dove prism is arranged between the third reflector and the second beam splitter prism, and the first dove prism and the second dove prism are rotated relative to each other by an angle of π / 2; The first CCD camera is arranged at the position where the first outgoing light of the second beam splitter prism emerges, and the first outgoing light is imaged to obtain a first interference image; the second CCD camera is arranged at the position where the second outgoing light of the second beam splitter prism emerges, and the second outgoing light is imaged to obtain a second interference image; An interference image is obtained, pre-processed, and then input into a convolutional neural network model to output a vortex light interference analysis map. The interference image is input into the convolutional neural network model, and the interference image features are first extracted through a multi-scale pyramid convolution module. Then, the interference image features are enhanced through a feature enhancement module to output an enhanced feature map. Finally, a cyclic memory fusion module is used to output a vortex light interference analysis map.

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